渤海湾盆地莱州湾凹陷沙三上段近源砂质辫状河三角洲沉积特征  

Sedimentary characteristics of near source sandy braided river delta in the upper 3rd member of Shahejie Formation in Laizhou Bay Sag,Bohai Bay Basin

作　　者：赵汉卿 李超 郭诚 陈晓明 张博 ZHAO Hanqing;LI Chao;GUO Cheng;CHEN Xiaoming;ZHANG Bo(Bohai Oilfield Research Institute,Tianjin Branch,CNOOC Ltd.,Tianjin 300459,China)

机构地区：[1]中海石油(中国)有限公司天津分公司渤海石油研究院,天津300459

出　　处：《世界地质》2024年第1期37-46,共10页World Geology

基　　金：国家重大科技专项(2011ZX05023-006-002);中海石油(中国)有限公司科技重大专项(YXKY-2018-TJ-04)。

摘　　要：为厘清渤海湾盆地莱州湾凹陷近源砂质辫状河三角洲沉积特征和储层发育规律,应用地震、钻测井资料、岩心观察及粒度分析等资料分析,总结K油田沙三上段的沉积特征。研究结果表明K油田沙三上段可识别出辫状河三角洲平原、辫状河三角洲前缘及辫状河前三角洲等3种亚相,进一步划分出辫状河道、冲积平原、水下分流河道、河口坝、席状砂及水下分流河道间等6种沉积微相,不同沉积微相的粒度分布特征明显不同;沙三上段发育一套完整的升降旋回,初期主要发育水下分流河道沉积,砂体储层厚度4~9 m,河道末端发育河口坝,砂体储层厚度3~8 m,分流河道平面分布范围最大,是该地区重要的储集层;之后湖平面逐渐上升,河口坝平面发育范围达到最大,至最大湖泛面后湖平面缓慢下降,并在沙三上段顶部发育辫状河三角洲平原亚相,砂岩厚度减薄至2~5 m。To elucidate the sedimentary characteristics and reservoir development patterns of the near source sandy braided river delta in the Laizhou Bay Sag of the Bohai Bay Basin,an analysis was conducted using seismic,drilling,logging data,core observations,and grain size analysis.This study summarized the sedimentary characteristics of the upper part of the 3rd member of the Shahejie Formation(E_(2)S_(3)^(U))in the K Oilfield.The results indicate that in the E_(2)S_(3)^(U) of the K Oilfield,three subfacies can be identified:the braided river delta plain,braided river delta front,and the braided river front delta.Six sedimentary microfacies are further distinguished:braided river channels,alluvial plains,underwater distributary channels,mouth bars,sheet sands,and underwater interdistributary channels.These microfacies exhibit distinct particle size distribution characteristics.A complete set of transgressive and regressive cycles is evident in E_(2)S_(3)^(U).Initially,sedimentation was dominated by underwater distributary channels with sand reservoir thicknesses ranging from 4 to 9 m.Mouth bars developed at the channel ends with reservoir thicknesses of 3 to 8 m.The distributary channels,having the widest planar distribution,constitute the key reservoirs in the area.Subsequently,as the lake level gradually rose,the extent of mouth bar development peaked.After reaching the maximum flooding surface,the lake level slowly declined,leading to the development of the braided river delta plain subfacies at the top of E_(2)S_(3)^(U),where the sandstone thickness reduced to 2 to 5 m.

关 键 词：沙三上段 辫状河三角洲 沉积特征 莱州湾凹陷 

分 类 号：P618.13[天文地球—矿床学]